Evaluation of Urban Expansion in Chongqing City based on the Nighttime Light Data

Urbanization is an important embodiment of regional economic development.Its progress reflects the level of economic development in the region.Since Chongqing being directly under the Central Government in 1997，it has enjoyed rapid economic growth and rapid urbanization.Looking for an intuitive and efficient method of urbanization is of great practical significance to correctly grasp the achievements of urbanization in Chongqing from the overall situation.Through the comparison of statistical data on night lighting data，we can extract the built-up area of Chongqing year after year.The city gravity model is based on the results.A night light index is established and used to calculate the speed of urban expansion.The result indicates that the urban distributions in Chongqing is spatially distributed and expanded in all directions.There are great differences between urban areas and rural areas and urban area urbanization level is higher.The city gravity gradually shifted from Yuzhong district to Yubei district.The speed of city expansion maintains high.Our study can afford refers for the planning and construction of the Chongqing city.